1. Field of the Invention
This invention relates to equipment for securing workpieces during a machining operation conducted with numerical-control equipment.
2. Description of the Prior Art
In the production of workpieces which have been subjected to some number of machining operations in order to produce, at (and precisely at) certain predetermined locations, certain predetermined desired machined features--holes of desired diameter and depth, slots, grooves, etc.--it is already well known to provide and use for such purposes some kind of so-called "numerical control" (NC) equipment, that is to say, equipment of a kind which includes not only the means for securing the workpiece and the drill or milling head or other tool for producing the desired features in the finished workpiece, but also a programmable computer means which will, in accordance with a program provided thereto, sequentially position and activate and de-activate the various tools that are to be brought into contact with the workpiece during a cycle of the operation thereof. When the task to be accomplished includes the making of some number of product workpieces which are intended to be as nearly identical and interchangeable as possible, which is often the case, the improvement in productivity which is obtainable with the use of such equipment, in contrast to the relative inefficiency of having the pieces made by a skilled machinist who repetitively performs the necessary manipulations, is immense. Given properly programmed NC equipment, a relatively unskilled machine operator can produce, in a remarkably short period of time, a number of machined workpieces which are reliably identical; the machinery operates--without error, hesitation, or interruption caused by fatigue or distraction--to subject each workpiece in its turn to the operation required.
The NC approach has proved to have its limitations, however, and there have already been developed some inventions which have been addressed to overcoming them.
It is known, for example, from U.S. Pat. No. 4,529,183, that in the case of the making of a plurality of workpieces which require more machining than can be done with one insertion of a workpiece into the NC equipment, there may be provided a "two-place" precision machine vise of the kind disclosed therein, a vise having a fixed central member which affords a fixed central reference point to each of two workpieces secured within the equipment. Such equipment is advantageously used, in accordance with the invention of the above-designated patent, by orienting the workpieces appropriately so that during one cycle of operation of the NC equipment, each workpiece undergoes the set of machining operations appropriate to its orientation, which thus makes it possible to produce a number of such product workpieces in a particularly advantageous and efficient manner by manipulating the equipment and the work fed to it in the manner described in the paragraph bridging columns 4 and 5 of said patent, thereby producing one finished workpiece for each cycle of operation of the equipment.
The device of the patent discussed above serves to locate a workpiece accurately with respect to only two datum planes, namely, the one afforded by the side of the fixed central jaw member and the one defined by the bed of the two-place precision machine vise. It is desirable to be able to position a workpiece accurately and quickly, without squaring or the use of an edge locator, with respect to yet a third datum plane, one which is mutually perpendicular to the other two and thus defines the location of the workpiece in a direction crosswise of the longitudinal axis of the two-place precision machine vise. In this regard, it has by now also become known, in accordance with U.S. Pat. No. 4,750,722, to address that problem by providing a supplemental precision machine vise, a smaller one, which may be mounted to the fixed central jaw of the main precision machine vise in place of the jaw plate thereof, or otherwise attached thereto.